Contributions to wafer pollution come in many forms and include substances drawn from the air, silt from soil erosion, chemical fertilizers and pesticides, runoff from septic tanks, outflow from livestock feedlots, chemical wastes from industries, and sewage and other urban wastes from cities and towns.
When organic matter exceeds the capacity of microorganisms in the water to break it down and recycle it, the excess of nutrients in such matter can encourage algal water blooms. When these algae die, their remains add further to the organic wastes already in the water, and eventually the water becomes deficient in oxygen. Organisms that do not require oxygen then attack the organic wastes, releasing gases such as methane and hydrogen sulfide, which are harmful to the oxygen-requiring forms of life. The result is a foul-smelling, waste-filled body of water.
Modern sewage systems include domestic and industrial sewers and storm sewers. Sewage treatment plants remove organic matter from waste water through a series of steps. As sewage enters the plant, large objects (such as wood and gravel) are screened out; grit and sand are then removed by settling or screening with finer mesh. The remaining sewage passes into primary sedimentation tanks where suspended solids (sludge) settle out. The remaining sewage is aerated and mixed with microorganisms to decompose organic matter. A secondary sedimentation tank allows any remaining solids to settle out; the remaining liquid effluent is discharged into a body of water. Sludge from the sedimentation tanks may be disposed of in landfills, dumped at sea, used as fertilizer, or decomposed further in heated tanks (digestion tanks) to produce methane gas to power the treatment plant.
Aquariums, both domestic and commercial suffer from the need to regularly replace the water due to the buildup of various toxins. For example, salt water aquariums generally need to have 25% to 75% of the water changed every 7 to 10 days with normal aquarium filters, although large bacteria filters usually the same size to three times larger than the tank can hold the same water for up to 3 months.
Biological filtration systems function by providing an area in a tank which is isolated from animals. The filter should have a high surface area (e.g. some biological filters use soft sponges, small plastic hollow balls full of holes or pebbles) for non-toxic bacteria to grow on which feed on ammonia and nitrite produced by the fishes waste. If this waste is not removed, fish may die within days. Generally, the water in salt water tanks must be changed every 7 to 10 days and the water in fresh water tanks, every 20 to 40 days depending on fish density. The amount of time between water changes from fresh water to salt water is different because salt water fish generally have a higher metabolism than fresh water fish.
The preceding discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia, or anywhere else, as at the priority date of the application.
Throughout the specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.